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Groups > linux.kernel > #1721114

[patch V3 06/44] x86/tracing: Introduce a static key for exception tracing

From Thomas Gleixner <tglx@linutronix.de>
Newsgroups linux.kernel
Subject [patch V3 06/44] x86/tracing: Introduce a static key for exception tracing
Date 2017-08-28 09:10 +0200
Message-ID <ujmlm-2xk-73@gated-at.bofh.it> (permalink)
References <ujmbD-2dY-5@gated-at.bofh.it>
Organization linux.* mail to news gateway

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Switching the IDT just for avoiding tracepoints creates a complete
impenetrable macro/inline/ifdef mess.

There is no point in avoiding tracepoints for most of the traps/exceptions.
For the more expensive tracepoints, like pagefaults, this can be handled with
an explicit static key.

Preparatory patch to remove the tracing idt.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/include/asm/trace/common.h      |   15 +++++++++++++++
 arch/x86/include/asm/trace/exceptions.h  |    4 +---
 arch/x86/include/asm/trace/irq_vectors.h |    4 +---
 arch/x86/kernel/tracepoint.c             |    9 ++++++++-
 4 files changed, 25 insertions(+), 7 deletions(-)

--- /dev/null
+++ b/arch/x86/include/asm/trace/common.h
@@ -0,0 +1,15 @@
+#ifndef _ASM_TRACE_COMMON_H
+#define _ASM_TRACE_COMMON_H
+
+extern int trace_irq_vector_regfunc(void);
+extern void trace_irq_vector_unregfunc(void);
+
+#ifdef CONFIG_TRACING
+DECLARE_STATIC_KEY_FALSE(trace_irqvectors_key);
+#define trace_irqvectors_enabled()			\
+	static_branch_unlikely(&trace_irqvectors_key)
+#else
+static inline bool trace_irqvectors_enabled(void) { return false; }
+#endif
+
+#endif
--- a/arch/x86/include/asm/trace/exceptions.h
+++ b/arch/x86/include/asm/trace/exceptions.h
@@ -5,9 +5,7 @@
 #define _TRACE_PAGE_FAULT_H
 
 #include <linux/tracepoint.h>
-
-extern int trace_irq_vector_regfunc(void);
-extern void trace_irq_vector_unregfunc(void);
+#include <asm/trace/common.h>
 
 DECLARE_EVENT_CLASS(x86_exceptions,
 
--- a/arch/x86/include/asm/trace/irq_vectors.h
+++ b/arch/x86/include/asm/trace/irq_vectors.h
@@ -5,9 +5,7 @@
 #define _TRACE_IRQ_VECTORS_H
 
 #include <linux/tracepoint.h>
-
-extern int trace_irq_vector_regfunc(void);
-extern void trace_irq_vector_unregfunc(void);
+#include <asm/trace/common.h>
 
 DECLARE_EVENT_CLASS(x86_irq_vector,
 
--- a/arch/x86/kernel/tracepoint.c
+++ b/arch/x86/kernel/tracepoint.c
@@ -4,9 +4,11 @@
  * Copyright (C) 2013 Seiji Aguchi <seiji.aguchi@hds.com>
  *
  */
+#include <linux/jump_label.h>
+#include <linux/atomic.h>
+
 #include <asm/hw_irq.h>
 #include <asm/desc.h>
-#include <linux/atomic.h>
 
 atomic_t trace_idt_ctr = ATOMIC_INIT(0);
 struct desc_ptr trace_idt_descr = { NR_VECTORS * 16 - 1,
@@ -15,6 +17,7 @@ struct desc_ptr trace_idt_descr = { NR_V
 /* No need to be aligned, but done to keep all IDTs defined the same way. */
 gate_desc trace_idt_table[NR_VECTORS] __page_aligned_bss;
 
+DEFINE_STATIC_KEY_FALSE(trace_irqvectors_key);
 static int trace_irq_vector_refcount;
 static DEFINE_MUTEX(irq_vector_mutex);
 
@@ -36,6 +39,8 @@ static void switch_idt(void *arg)
 
 int trace_irq_vector_regfunc(void)
 {
+	static_branch_inc(&trace_irqvectors_key);
+
 	mutex_lock(&irq_vector_mutex);
 	if (!trace_irq_vector_refcount) {
 		set_trace_idt_ctr(1);
@@ -49,6 +54,8 @@ int trace_irq_vector_regfunc(void)
 
 void trace_irq_vector_unregfunc(void)
 {
+	static_branch_dec(&trace_irqvectors_key);
+
 	mutex_lock(&irq_vector_mutex);
 	trace_irq_vector_refcount--;
 	if (!trace_irq_vector_refcount) {

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Thread

[patch V3 00/44] x86: Cleanup IDT code Thomas Gleixner <tglx@linutronix.de> - 2017-08-28 09:10 +0200
  [patch V3 13/44] x86/mce: Remove duplicated tracing interrupt code Thomas Gleixner <tglx@linutronix.de> - 2017-08-28 09:10 +0200
    [tip:x86/apic] x86/mce: Remove duplicated tracing interrupt code tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-08-29 13:20 +0200
  [patch V3 05/44] x86/boot: Move EISA setup to a proper place Thomas Gleixner <tglx@linutronix.de> - 2017-08-28 09:10 +0200
    [tip:x86/apic] x86/boot: Move EISA setup to a separate file tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-08-29 13:20 +0200
  [patch V3 15/44] x86/smp: Use static key for reschedule interrupt  tracing Thomas Gleixner <tglx@linutronix.de> - 2017-08-28 09:10 +0200
    [tip:x86/apic] x86/smp: Use static key for reschedule interrupt  tracing tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-08-29 13:20 +0200
  [patch V3 12/44] x86/irqwork: Get rid of duplicated tracing interrupt  code Thomas Gleixner <tglx@linutronix.de> - 2017-08-28 09:10 +0200
    [tip:x86/apic] x86/irqwork: Get rid of duplicated tracing interrupt  code tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-08-29 13:20 +0200
  [patch V3 10/44] x86/irq: Get rid of duplicated  trace_x86_platform_ipi() code Thomas Gleixner <tglx@linutronix.de> - 2017-08-28 09:10 +0200
    [tip:x86/apic] x86/irq: Get rid of duplicated  trace_x86_platform_ipi() code tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-08-29 13:20 +0200
  [patch V3 06/44] x86/tracing: Introduce a static key for exception  tracing Thomas Gleixner <tglx@linutronix.de> - 2017-08-28 09:10 +0200
    [tip:x86/apic] x86/tracing: Introduce a static key for exception  tracing tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-08-29 13:20 +0200
  [patch V3 08/44] x86/apic: Remove the duplicated tracing version of  local_timer_interrupt Thomas Gleixner <tglx@linutronix.de> - 2017-08-28 09:10 +0200
    [tip:x86/apic] x86/apic: Remove the duplicated tracing version of  local_timer_interrupt() tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-08-29 13:20 +0200
  [patch V3 14/44] x86/smp: Remove pointless duplicated interrupt code Thomas Gleixner <tglx@linutronix.de> - 2017-08-28 09:10 +0200
    [tip:x86/apic] x86/smp: Remove pointless duplicated interrupt code tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-08-29 13:20 +0200
  [patch V3 04/44] x86/irq: Remove duplicated used_vectors definition Thomas Gleixner <tglx@linutronix.de> - 2017-08-28 09:10 +0200
    [tip:x86/apic] x86/irq: Remove duplicated used_vectors definition tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-08-29 13:20 +0200
  [patch V3 03/44] x86/irq: Get rid of the first_system_vector bogisity Thomas Gleixner <tglx@linutronix.de> - 2017-08-28 09:10 +0200
    [tip:x86/apic] x86/irq: Get rid of the 'first_system_vector'  indirection bogosity tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-08-29 13:20 +0200
  [patch V3 28/44] x86/idt: Create file for IDT related code Thomas Gleixner <tglx@linutronix.de> - 2017-08-28 09:10 +0200
    [tip:x86/apic] x86/idt: Create file for IDT related code tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-08-29 13:30 +0200

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